In Portugal's Douro Valley, the Port harvest is under way at Taylor's Quinta de Vargellas. Hairy-legged men in crimson-spattered underpants tread the native red grapes under foot. At Freemark Abbey in California's Napa Valley, Ted Edwards monitors satellite imaging technology to help him work out the optimum time to pick the cabernet sauvignon. Meanwhile, in Chile's Maipo Valley, Alvaro Espinoza surveys the moon and buries a dung-filled cow-horn to release planetary energy in the cultivation of the vine. Autumn in the world's vineyards embraces ancient traditions, hi-tech innovations, and sophisticated biodynamic practices that signal a return to nature. Welcome to the science and anti-science of wine.

Since time immemorial the natural bloom on the grape kick-started fermentation and lo, with a bit of intervention to stop it souring into vinegar, we had wine. Today, as white-coated boffins bring problems of oxidation, volatile acidity, reduction and cork taint within their sights, science is moving into the realms of science-fiction. The Portuguese have developed robot treaders to replace human beings. In France, where genetically modified crops are derided by protesters as Frankenfoods, experiments have been authorised for GM vines to halt the spread of the fanleaf virus that attacks vine roots. A biotechnologist at Stellenbosch University claims GM wines might prevent hangovers.

In the cellar, sulphur dioxide (to neutralise bacteria), filtering and cooling technology are part and parcel of the modern winemaker's bag of tricks. If a wine is over-alcoholic because of a new vine clone or yeast strain, technology can ride to the rescue in the form of alcohol-reducing methods such as reverse osmosis or spinning cone technology. Jamie Goode's recently published, stimulating and highly approachable Wine Science (£30, Mitchell Beazley) will explain all. Even wine-tasting has become a science with "nosing" machines built to replicate the complexities of the human olfactory system. Fortunately for this human, the technology's still at an early stage. Meanwhile, one advance I strongly favour is screwcaps instead of corks to keep wine fresh.

Almost every winery worth its salt today is constructed to optimise innovation and function, and to reduce the very real dangers of infection in wine. The latest buzzword, gravity flow, involves architects in devising ways of building wineries into hillsides to allow the wine to flow naturally.

Used properly, technology can be harnessed to help us understand why time-honoured practices work - or don't. But the less desirable consequences can be corner-cutting: spraying without thinking, increased yields that compromise quality, excessive filtering.

In a world that demands reliability, it is arguable whether today's sophisticated technology is used less as a means of achieving quality and more to iron out the peaks and troughs of vintage variation for the sake of consistency. Or, worse, to make up for lack of hygiene in the winery and human error.

In reaction to too much technology and chemical spraying there has been a return to tradition and natural techniques. Not that an absence of science necessarily means better wine. The reduction of sulphur, a return to wild yeasts and the use of new oak barrels can all cause problems in the cellar. Like the telling of a good joke, proper use of tehchnology in wine is not about the what but the how.

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